Adjusted valgrind-check Containerfile to ensure apt update and install are linked and cached together in one layer

Otherwise, the update layer can be cached and have bad information for the subsequent two install command layers.

As the distribution changes package versions the install layers, if they are not cached, will fail.

Also combined the two install commands into one for brevity.

Ticket: ENT-13252
Changelog: none
(cherry picked from commit c6e385d)

 Conflicts:
	tests/valgrind-check/Containerfile

To get a smaller change I just combined the update and install apt lines instead of also changing the ubuntu version and package list.

Author: craigcomstock

tests/valgrind-check/Containerfile

@@ -1,7 +1,6 @@
 FROM ubuntu:20.04 AS build
-RUN DEBIAN_FRONTEND=noninteractive apt-get update -y --fix-missing
-RUN DEBIAN_FRONTEND=noninteractive apt-get install -y libssl-dev libxml2-dev libpam0g-dev liblmdb-dev libacl1-dev libpcre3 libpcre3-dev
-RUN DEBIAN_FRONTEND=noninteractive apt-get install -y python git flex bison byacc automake make autoconf libtool valgrind curl
+RUN DEBIAN_FRONTEND=noninteractive apt-get update -y --fix-missing \
+ DEBIAN_FRONTEND=noninteractive apt-get install -y libssl-dev libxml2-dev libpam0g-dev liblmdb-dev libacl1-dev libpcre3 libpcre3-dev python git flex bison byacc automake make autoconf libtool valgrind curl
 COPY masterfiles masterfiles
 COPY core core
 WORKDIR core